JP2005510123A - Communication in asynchronous wireless networks - Google Patents

Abstract

PROBLEM TO BE SOLVED: To communicate in an asynchronous wireless network.
A system and technique for setting a reference value corresponding to a timing of a signal received from a first source and for determining a timing for each of signals received from a plurality of second sources; 2 to adjust the reference value to the timing of the signal received from 1 of the two sources, the timing of the received signal being used to adjust the reference value so that the time is closest to the unadjusted reference value. , And for synchronizing the signal to a reference value for transmission. It is emphasized that this summary is given according to rules that require a summary that allows searchers and other readers to quickly review the subject matter of the technical disclosure. It is stated with an understanding that it is not used to explain or limit the scope or meaning of the claims.

Description

  This application is filed under US Patent Law 35 U.S. Patent No. 60 / 337,472, filed Nov. 9, 2001. S. C. Claim priority under §119 (e). The contents of which are incorporated herein by reference.

  The present invention relates to a communication system, and more particularly to a system and technique for synchronizing a communication device to an asynchronous network access point.

  Modern communication systems are designed to allow multiple users to share a common communication medium. One such communication system is a code division multiple access (CDAM) system. A CDMA communication system is a modulation and multiple access scheme based on spread spectrum communication. In a CDMA communication system, multiple signals share the same frequency spectrum, thus providing increased user capacity. This is accomplished by sending each signal using a different code. The code modulates the carrier and thereby spreads the spectrum of the signal waveform. The transmitted signal is separated in the receiver by a correlator that uses the corresponding code to despread the spectrum of the signal. Unsolicited signals that do not match the code are not despread in the bandwidth and simply contribute as noise.

  In a CDMA communication system, a user can access the network or communicate with other users via a network access point. A network access point typically includes a radio network controller that supports multiple nodes. For the purposes of this disclosure, the term “node” is used to refer to a Node B, a base station, or any other similar communication station. Each node is assigned to work for all users in an area commonly referred to as a cell or sector. Within any given area, a user may communicate with any number of adjacent nodes as well as nodes working in that area.

  In some CDMA communication systems, the nodes are synchronized with each other. As an example, the Navstar Global Positioning satellite navigation system is often used to synchronize nodes to a common time reference value. As a result, once a user captures and synchronizes with a node, the user can communicate with another node in synchronization with the movement from region to region. This is in contrast to asynchronous CDMA communication systems. Asynchronous CDMA communication systems may require users to resynchronize to different nodes as they move across different regions of coverage. The resynchronization process must be performed quickly and minimizes possible interruptions in communication that the user can withstand. In addition, it is advantageous for the user to minimize the time during the resynchronization process, as this reduces the risk of the radio communication link falling to other nodes other than the reference node, and the propagation delay More accurate position estimates based on measurements.

[summary]
In one aspect of the invention, a method of communication sets a reference value corresponding to a timing of a signal received from a first source and determines a timing for each of signals received from a plurality of second sources. The reference value is adjusted to the timing of the received signal from 1 of the second source, and the timing of the received signal is adjusted so that the time is closest to the unadjusted reference value. And synchronizing the signal to a reference value for transmission.

  In another aspect of the invention, the apparatus is for setting a reference value corresponding to the timing of a signal received from a first source and for determining timing for each of the signals received from a plurality of second sources. In order to adjust the reference value to the timing of the received signal from 1 of the second source, the reference value is adjusted so that the time of the received signal is closest to the unadjusted reference value. And configured to synchronize the signal to a reference value for transmission.

  In yet another aspect of the invention, a computer-readable medium incorporating a program of instructions executable by a computer that implements a method of communication, the method comprising: timing of a signal received from a first source; Setting a reference value corresponding to, determining the timing for each of the signals received from the plurality of second sources, and adjusting the reference value to the timing of the signal received from 1 of the second source The timing of the received signal is used to adjust the reference value so that the time is closest to the unadjusted reference value, and includes synchronizing the signal to the reference value for transmission.

  In a further aspect of the invention, the apparatus determines a reference means for setting a reference value corresponding to the timing of the signal received from the first source and the timing for each of the signals received from the plurality of second sources. And adjusting means for adjusting the reference value to the timing of the signal received from 1 of the second source so that the timing of the received signal is closest to the unadjusted reference value. And includes means for synchronizing the signal to the reference value for transmission.

  It is understood that other embodiments of the present invention will be readily realized by those skilled in the art from the following detailed description. Only illustrative embodiments of the invention are shown and described here for purposes of explanation. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of various other related modifications, all without departing from the spirit and scope of the invention. . Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

  The aspects of the invention are illustrated by way of example in the accompanying drawings and are not limiting.

  The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments in which the invention may be practiced. The term “exemplary” used consistently in this description means “act as an example, instance, or illustration”. Any embodiment disclosed herein as “exemplary” need not be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without the use of these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present invention.

  While various aspects of the present invention will be described in the context of a CDMA communication system, those skilled in the art will appreciate that these aspects are equally applicable for use in various other communication environments. You will appreciate the value. Accordingly, any reference to a CDMA communication system is intended only to illustrate the inventive aspects of the present invention, with the understanding that such aspects of the invention have a wide range of applications.

  FIG. 1 is a functional block diagram of an asynchronous CDMA communication system. The radio network controller 102 can be used to provide an interface between the network 104 and all nodes 106a-d distributed throughout the geographic region. A geographical area is generally divided into areas known as cells or sectors. Nodes are assigned to be used by all users in a region. User equipment 108 may access network 104 or may communicate with other user equipment via one or more nodes under the control of radio network controller 102. If the user device 108 is in communication with one or more nodes, the user device 108 selects the reference node as a synchronization source for transmission to all notes. As the user equipment 108 moves away from the reference node, the user equipment eventually needs to select a new node as the synchronization source. The user equipment can select the node that requires the least amount of slewing to resynchronize the transmission. Slewing refers to the process of adjusting the user equipment transmit signal timing to synchronize with a new synchronization source. To minimize slewing, the user equipment can select the node whose signal is received in the time closest to the signal received from the previous reference node.

  An exemplary asynchronous CDMA communication system was proposed by a consortium named “3rd Generation Partnership Project”, referred to herein as 3GPP, and here referred to as document numbers 3GPP TS21.101, 3GPP TS25.211, referred to as the W-CDMA standard. Can be designed to support standard FDD mode operations specifically shown in a set of documents including 3GPP TS 25.212, 3GPP TS 25.213, 3GPP TS 25.214, and 3GPP TS 25.133 . The W-CDMA standard is specifically incorporated herein by reference. The W-CDMA specification published by 3GPP is an official record and is well known in the art. W-CDMA (also known as UTRA-FDD) is adopted and published as a regional standard by various standards bodies, for example, by the European Telecommunications Standards Institute (ETSI). The 3GPP specification describes the use of a combination of physical channels SCH and CPICH transmitted by each node in a W-CDMA communication system. The SCH and CPICH can be used by the user equipment and synchronize with different nodes as the user equipment moves through the coverage area.

  FIG. 2 is a diagram illustrating a downlink frame structure for physical channels SCH, CPICH, and P-CCPCH transmitted by a node in the W-CDMA communication system. Frame 202 can be of any duration depending on the specific application and overall design constraints. In the exemplary W-CDMA communication system described, the frame period is 10 milliseconds and includes 38,400 chips. The frame can be divided into 15 slots 204, each slot having 2560 chips. Each slot 204 can be further divided into ten parts 206, each part having 256 chips.

  The SCH and P-CCPCH are time multiplexed. Only the SCH is transmitted during the first part of each slot 204, and the P-CCPCH is transmitted only between parts 2 through 10 of each slot. CPICH is transmitted in parallel with SCH and P-CCPCH. The frame timing for SCH, P-CCPCH and CPICH is the same. The SCH is subdivided into a primary SCH carrying a primary synchronization code (PSC) sequence and a secondary SCH carrying a secondary synchronization code (SSC) sequence. PSC and SSC sequences are orthogonal to each other. These are generated using a generalized hierarchical systemized Golay and Hadarmard sequence and transmitted at the beginning of each other. The PSC sequence is the same sequence for each slot in the communication area and for each node. The SSC sequence can be one of 16 possible sequences in each slot. The P-CCPCH carries broadcast data such as the identity of the transmitting node and other information that is general to all user equipment communicating with that node. In parallel with SCH and P-CCPCH, CPICH is continuously transmitted. CPICH carries a pilot signal known a priori (based on theory). The pilot signal can be used by the user equipment to be synchronized to the node, and once the user equipment is synchronized to the node and successfully completes an access attempt to the system, the data sent to the user equipment is made coherent. Acts as a phase reference value for demodulation.

  The pilot signal contains no data and is often characterized as an unmodulated spread spectrum signal. The pilot signal from each node is generally spread with the same orthogonal code, but scrambled with a main scrambling code specific to the node. The main scrambling code is truncated at the end of each CPICH frame and then repeated from the beginning at the start of each frame. In an exemplary W-CDMA communication system, there are 512 possible main scrambling codes for a given node. The P-CCPCH is also scrambled with the main scrambling code. The main scrambling code used by the node is not known a priori by the user equipment.

  FIG. 3 is a functional block diagram illustrating generation of SCH, P-CCPCH, and CPICH channels by a node. The PSC generator 302 can be used to generate a PSC sequence comprising a predetermined 256 chip sequence used in a user equipment for node slot timing acquisition. The SSC generator 304 can be used to generate an SSC sequence. The SSC sequence serves two functions. First, the SSC sequence is used at the user equipment to identify the frame timing of the node. Second, the SSC sequence also provides a code group identifier that identifies a group of eight possible main scrambling codes. In a W-CDMA communication system using 512 possible primary scrambling codes, there are 64 code group identifiers. The SSC generator 304 first maps the group identifier to 64 possible 15 element codewords, and then assigns each codeword element that can have 16 different possible values to 16 Maps to one of the possible 256 chip sequences. Each of the 16 possible 256 chip sequences is orthogonal to each other, similar to the PSC sequence. A summer 306 can be used to combine each of the 16 256-chip SSC sequences with the PSC sequence. The puncture element 308 can be used to puncture the PSC and SSC sequences from the summer 306 into the first part of each slot. The main scrambling code generator 310 can be used to generate a main scrambling code for a node. The broadcast data can then be scrambled with the main scrambling code using multiplier 312 and punctured to parts 2-10 of each slot using puncture element 308. The orthogonal code generator 314 can be used to generate the CPICH. The CPICH can then be scrambled with the main scrambling code using multiplier 316. The scrambled CPICH can be combined with the SCH using scrambled P-CCPCH from puncture element 308 as well as other downlink channels using summer 318.

  FIG. 4 is a functional block diagram of an exemplary user device that operates in a W-CDMA communication environment. An RF analog front end (AFE) 402 connected to one or more antennas 404 can be used to support a node's wireless communication link. In the reception mode, a signal transmitted from the node is connected from the antenna 404 to the AFE 402. AFE filters and amplifies the signal, downconverts the signal to baseband, and digitizes the baseband signal.

  The digital baseband signal is provided to searcher 406 for acquisition and synchronization purposes. Node slot timing acquisition involves searching through a digital baseband signal to find a PSC sequence embedded in the SCH. This can be achieved by correlating the baseband signal with a locally generated PSC sequence. In a method described in more detail later, the frame timing can be extracted from the SSC sequence and which of the 64 possible code groups belong to the node's primary scrambling code. Can be used to determine. Knowing the code group of the main scrambling code, the searcher 406 can determine which main scrambling code is actually being used by the node. This can be achieved by correlating the digital baseband signal with 8 versions of the a priori known pilot signal. The pilot signal is generated by scrambling with the 8 possible primary scrambling codes of the code group and by selecting the one that produces the most energy in the correlation output. With information on slot timing, frame timing and main scrambling code, the user equipment can use CPICH for channel estimation and coherent demodulation of data transmitted to the user equipment.

  The digital baseband signal is also provided to the receiver 407. The receiver includes a demodulator 408 and a decoder 410. The demodulator 408 can be implemented in various ways. As an example, a rake receiver may be used in a W-CDMA communication system, or any other type of communication system that uses diversity techniques to overcome fading. Rake receivers typically employ multipath independent fading that can be separated to achieve diversity gain. This can be achieved through an integrated attempt between the searcher 406 and the rake receiver. In particular, the searcher 406 can be configured to identify strong multipath arrivals of pilot signals. The fingers can then be assigned by the searcher 406 to identify multipath timing offsets. The fingers may be used by the rake receiver as a timing reference value to correlate traffic for each expected multipath reflection. The separate correlations can then be coherently integrated and provided to the decoder 410 for deinterleaving, decoding, and frame check functions.

  The user equipment also includes a transmitter 411 to support the transmission mode. The transmitter 411 includes a data queue 412, an encoder 414, and a modulator 416. The data queue 412 can be used to buffer data that the user equipment intends to transmit to the node. The frame timing information derived by the searcher 406 can be used to release traffic from the data queue 412 with a time offset from the corresponding downlink frame. In the W-CDMA communication system, data is released from the data queue 412 in the following manner. The method generates 1024 chip offsets from the reception of a frame via a downlink first detectable multipath from a reference node involved in transmission of the corresponding frame in the uplink. However, any offset may be used depending on the particular application and overall design parameters.

  Data from data queue 412 is provided to encoder 414 for encoding, interleaving and frame check functions. The encoded data from encoder 414 is then supplied to a modulator 416 that spreads the data with orthogonal codes. The modulated data is then filtered, upconverted, amplified and fed to the AFE 402 connected to the antenna 404.

  FIG. 5 is a diagram of user equipment operating in a multi-node W-CDMA communication environment. In a W-CDMA communication environment, four nodes 502a-d are shown. Each node 502a-d transmits a pilot signal throughout its respective communicable area 504a-d. The pilot signals transmitted by each node 502a-d are spread with the same orthogonal code, but scrambled using different main scrambling codes. The main scrambling code allows the pilot signals to be distinguished from each other and therefore identifies the originating node 502a-d. The user device 506 is shown by a series of broken lines passing through different communicable areas. It is shown that the user device 506 first passes through the first communicable area 504a. Assume that user equipment 506 is attempting to establish communication with the network. From the first coverage area 504a, the user equipment 506 looks for SCH and CPICH for acquisition and synchronization as previously described. After this is achieved, user equipment 506 determines the quality of the wireless communication link to the node by measuring the strength of the pilot signal from the node. If the strength of the pilot signal exceeds the threshold, for a pilot signal from the first node 502a, the user equipment 506 attempts to access that node 502a. Depending on the available resources, node 502a can establish a wireless communication link to user equipment 506 for downlink traffic transmission. After the access attempt is successfully completed, the user equipment 506 adds its node 502a to its active set and establishes a wireless communication link to transmit traffic to that node. At this point, only node 502 a is a member of the active set of user device 506. The user equipment 506 also uses the node 502a as a reference value for synchronizing the confident uplink frame.

  When the user apparatus 506 moves to an area where the first and second communicable areas 504a-b overlap, the strength of the pilot signal from the second node 502b increases until the threshold is exceeded. As a result, the second node 502b may be added as an active set of user equipment 506, and another wireless communication link is established. In that case, the user equipment 506 communicates with both the first and second nodes 502a-b, but the transmission of uplink frames by the user equipment 506 remains synchronized to the reference node 502a.

  When the user equipment 506 moves out of the first coverage area 504a, the strength of the pilot signal from the first node 502a causes the reference node 502a to be removed from the active set of the user equipment 506. Decreases until it falls below the threshold. In at least one embodiment, the reference node is not removed from the active set as soon as the pilot signal strength drops below a threshold. Rather, the pilot signal strength should remain below the threshold for a predetermined time before the reference node is removed from the active set. This approach reduces the likelihood that the reference node will be removed from the active set of the user equipment because the spurious signal level fluctuates. Once the reference node 502a is removed from the active set of user equipment 506, the wireless communication link between the two is weak. Then, the user equipment 506 uses the frame timing information extracted from the PSC embedded in the SCH channel and the multipath timing set from the SSC sequence and the CPICH of the second node 502b to use the second node 502b. Resynchronize the timing of the uplink frame to the downlink frame from The second node 502b is now a reference node.

  When the user device 506 further moves toward the final destination, the user device 506 moves to an area where the second, third, and fourth communicable areas 504b-d overlap. In this region, the strength of the pilot signal from the third and fourth nodes 502c-d increases until the respective strength exceeds the threshold. As a result, the third and fourth nodes 502c-d may be added to the active set of the user equipment 506, and the wireless communication link is between the user equipment 506 and the third and fourth nodes 502c-d, respectively. Established between. In this case, the user equipment 506 communicates with the second, third and fourth nodes 502b-d, but the transmission of the uplink frame remains synchronized with the second node 502b.

  When the user device 506 is synchronized with the second node 502b, as the user device 506 moves out of the second communicable area 504b, which of the two nodes 502c-d becomes a reference node, There is uncertainty about which to choose. This ambiguity can be resolved in a variety of ways. As an example, user equipment 506 can resynchronize to a node that requires the least amount of slewing. In particular, the user equipment 506 is closest in time to the start of the first multipath arrival of the same downlink frame previously received from the second node 502b, the first multipath arrival of the start of the downlink frame. Can resynchronize to the node.

  FIG. 6 is a functional block diagram of an exemplary searcher that can be used in the user apparatus of FIG. The searcher includes a PSC detector 602. Since the PSC sequence is the same for each slot, the PSC detector 602 correlates the received digital baseband signal with a locally generated replica of the PSC sequence by methods well known in the art. Slot timing can be estimated.

  SSC detector 604 can be used to decode SSC sequences by methods well known in the art. In particular, the SSC detector 604 correlates the SSC sequence in each slot (which can be one of 16 possible sequences) over one or more frames, and the 16 codeword elements To decide. Based on the resulting codeword, the SSC detector 604 can determine the first slot in the frame and can use the slot timing information from the PSC detector 602 to determine the frame timing. . The SSC detector 604 can also demap the codeword to a code group identifier for the main scrambling code of the node.

  Pilot detector 606 can be used to correlate the digital baseband signal with a locally generated scrambled orthogonal code. Orthogonal code generator 608 can be used to generate eight possible scrambled orthogonal codes for the code group to which a node is assigned based on the code group identifier from SSC detector 604. It is. In a manner well known in the art, one or more slots of the received digital baseband signal can be correlated with 8 possible orthogonal codes until a pilot signal is detected.

  As a result of this process, multiple copies of the pilot signal from the node may be detected at different times due to multipath reflections. Timing generator 610 can be used to detect multipaths in the pilot signal and thus can assign fingers to a rake receiver (not shown). In communication including a plurality of nodes, the frame timing of each node in the active set may be given to the selector 612. Timing generator 610 can be used to select the frame timing for the first multipath arrival from the reference node. The selected frame timing is provided to an offset generator 614 to delay uplink transmission from receipt of the corresponding downlink frame. In the exemplary embodiment described, any delay may be used depending on the particular application and overall design constraints, but the delay is 1024 chips. The offset generator 614 can thus be used to delay the release of data from the data queue 412 (see FIG. 4). The offset generator 614 should be set to a delay that is less than the desired delay, causing processing delays for the searcher 406, encoder 414, modulator 416, and AFE 402 (see FIG. 4).

  During traffic communication between the node and the user equipment, the pilot detector 606 continues to search for new pilot signals. Once a new pilot signal with sufficient strength is detected, its originating node can be added to the active set. At the same time, the pilot detector 606 continues to monitor the pilot signal from the active node using the specific main scrambling code set for each pilot signal during acquisition. If the pilot signal from any node falls below a predetermined threshold during an extended period of time, that node should be removed from the active set. If the pilot signal from the reference node falls below a predetermined threshold, the pilot detector 606 can cause the timing generator 610 to select a new node as the timing reference value from the active set. . Assuming that two or more nodes remain active, timing generator 610 should select the node that requires the least amount of slewing. This is because the timing generator 610 determines which node the first multipath arrival for which downlink frame is closest in time to the first multipath arrival for the downlink frame previously transmitted from the previous reference node. Means you should choose. This selection criterion should be able to be adopted even when no more frame timing information from the SCH for the previous reference node is available. This can be achieved in various ways. In user equipment with a rake receiver, the finger assignment for the previous reference node can be used to select the appropriate node for resynchronization. Alternatively, frame timing for uplink transmission can be used to select an appropriate node for resynchronization. Specifically, for the latter approach, the timing generator 610 can be used to set a reference value corresponding to the frame timing of the uplink transmission. The reference value moves faster in time by 1024 chips and derives the first multipath arrival for the downlink frame from the previous reference node. This approach is an attractive solution because the frame timing for uplink transmission can be determined even when there are no more finger assignments to the previous reference node.

  Regardless of the method, the timing generator 610 selects a new node as a reference value to resynchronize its transmission. The selector 612 can be used to select the frame timing for the first multipath arrival from the reference node. The selected frame timing can be provided to an offset generator 614 to delay uplink transmission from receipt of the corresponding downlink frame from the new reference node. A trigger from the offset generator 614 can be used to release traffic from the data queue 412 in the transmitter 411 (see FIG. 4). Adjustment of uplink transmission timing during resynchronization should be smooth rather than instantaneous. Otherwise, the node receiver should not be able to track this change in transmission timing.

  Various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein are general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gates. Can be implemented or implemented in an array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware elements, or any combination thereof designed to perform the functions described herein. . A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor can be implemented as a combination of computing devices. For example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

  The methods or algorithms described in connection with the embodiments disclosed herein may be implemented directly in hardware, in software modules executed by a processor, or in a combination of both. Software modules reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other storage medium known in the art it can. An exemplary storage medium is connected to a processor so that the processor can read information from and write information to the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can exist in the ASIC. The ASIC can exist in the user terminal. In the alternative, the processor and the storage medium may reside as a single element in a user terminal.

  The previous description of the disclosed embodiments allows anyone with knowledge in the art to make or use the present invention. Various modifications of these embodiments will be readily realized by those skilled in the art. The general principles defined herein can be applied to other embodiments without departing from the spirit and version of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be applied in a broad range consistent with the principles and superior characteristics disclosed herein.

FIG. 1 is a conceptual overview of an exemplary asynchronous CDMA communication system. FIG. 2 illustrates an exemplary downlink frame structure for a synchronous channel (SCH), a main common control physical channel (P-CCPCH), and a common pilot channel (CPICH) transmitted by nodes in an asynchronous CDMA communication system. It is. FIG. 3 is a functional block diagram illustrating generation of a synchronization channel (SCH), a main common control physical channel (P-CCPCH), and a common pilot channel (CPICH) by an exemplary node in an asynchronous CDMA communication system. FIG. 4 is a conceptual overview of an exemplary user device operating in an asynchronous CDMA communication system. FIG. 5 is a functional block diagram of an exemplary user equipment for use in an asynchronous CDMA communication system. as well as FIG. 6 is a functional block diagram of an exemplary searcher that can be used in the user apparatus of FIG.

Explanation of symbols

202 ... frame, 204 ... slot, 312, 316 ... multiplier, 404 ... antenna, 504A to D ... communicable area, 506 ... user equipment.

Claims (48)

A method of communication comprising:
Setting a reference value corresponding to the timing of the signal received from the first source;
Determining a timing for each of the signals received from the plurality of second sources;
Adjusting the reference value to the timing of the signal received from 1 of the second source, so that the timing of the received signal is adjusted so that the time is closest to the unadjusted reference value Used; and to synchronize the signal to a reference value for transmission.   The method of claim 1, wherein the reference value is adjusted after no more signals from the first source are received.   The method of claim 2, wherein adjusting the reference value comprises using the timing of the synchronized signal to determine the reference value after no more signals from the first source are received. To do.   The method of claim 1, wherein the signal received from the first source comprises a frame and the unadjusted reference value corresponds to the start of the frame.   5. The method of claim 4, wherein the signals received from the second source each comprise a frame, and the adjusted reference value is relative to one of the second sources that is closest in time to the unadjusted reference value. Corresponds to the start of the frame.   6. The method of claim 5, wherein the synchronized signal is transmitted after the reference value.   2. The method of claim 1, wherein the signal received from the first source comprises a plurality of multipath arrivals, wherein the unadjusted reference value corresponds to the first multipath arrival in time. .   8. The method of claim 7, wherein the signal received from the second source each comprises a plurality of multipath arrivals, wherein the adjusted reference value is closest in time to the unadjusted reference value. Corresponds to one multipath arrival of the second source.   9. The method of claim 8, wherein the signals received from the first and second sources each comprise a frame, wherein the unadjusted reference value is the first of the signals received from the first source. And the adjusted reference value corresponds to the start of the frame for the first multipath arrival for one of the second sources closest in time to the unadjusted reference value. Correspond.   10. The method of claim 9, wherein the synchronized signal is transmitted after the reference value.   10. The method of claim 9, wherein the signals received from the first and second sources each comprise a pilot signal, the method using the respective pilot signals from the first and second sources. Determining the timing of multipath arrival and using the determined timing to demodulate signals received from the first and second sources, wherein adjusting the reference value comprises: Using the multipath arrival timing to identify the first multipath arrival of the second source that is closest in time to the unadjusted reference value. A device comprising:
A signal received from 1 of the second source, for setting a reference value corresponding to the timing of the signal received from the first source, for determining a timing for each of the signals received from the plurality of second sources The timing of the received signal is used to adjust the reference value so that the time is closest to the unadjusted reference value, and to the reference value for transmission. Searcher configured to synchronize signals.   13. The apparatus of claim 12, further comprising a receiver configured to receive signals from the first and second sources.   The apparatus of claim 12, further comprising a transmitter configured to transmit the synchronized signal.   15. The apparatus of claim 14, wherein the synchronized signal is transmitted after the reference value.   16. The apparatus of claim 15, wherein the searcher further comprises an offset generator configured to generate a time delayed trigger from a reference value, wherein the trigger is used to transmit a synchronized signal. .   17. The apparatus of claim 16, wherein the transmitter further comprises a data buffer configured to store the synchronized signal, the data buffer receiving the synchronized signal for transmission in response to the trigger. Configured to discharge.   The apparatus of claim 12, wherein the searcher is further configured to adjust the reference value after no more signals from the first source are received.   19. The apparatus of claim 18, wherein the searcher is further configured to determine an adjustment of the reference value from the timing of the synchronized signal after no more signals from the first source are received.   13. The apparatus of claim 12, wherein the signal received from the first source comprises a frame, and wherein the searcher is further configured to set a reference value to coincide with the start of the frame. .   21. The apparatus of claim 20, wherein the signals received from the second source each comprise a frame, and wherein the searcher is for one of the second sources closest in time to an unadjusted reference value. Further configured to adjust the reference value to coincide with the start of the frame.   13. The apparatus of claim 12, wherein the signal received from the first source comprises a plurality of multipath arrivals, wherein the searcher matches the first multipath arrival in time. Further configured to set   23. The apparatus of claim 22, wherein a signal received from a second source each comprises a plurality of multipath arrivals, wherein the searcher is the second closest to the unadjusted reference value in time. Further configured to adjust the reference value to match one first multipath arrival of the source.   24. The apparatus of claim 23, wherein the signals received from the first and second sources each comprise a frame, and wherein the searcher is a first multipath arrival of signals received from the first source. To set the reference value to match the start of the frame for, and to match the start of the frame for the first multipath arrival for one of the second sources closest in time to the unadjusted reference value Further configured to adjust the reference value.   24. The apparatus of claim 23, wherein the signals received from the first and second sources each comprise a pilot signal, and wherein the searcher uses the first and second pilot signals, respectively. Further configured to determine the timing of multipath arrival from the source, the apparatus for demodulating signals received from the first and second sources using the multipath arrival timing determined by the searcher And wherein the searcher is referred to by using the determined timing of multipath arrival for one of the second sources closest in time to the unadjusted reference value. Further configured to determine the adjustment of the signal. A computer readable medium incorporating a program of instructions executable by a computer program for carrying out a method of communication, the method comprising:
Setting a reference value corresponding to the timing of the signal received from the first source;
Determining a timing for each of the signals received from the plurality of second sources;
Adjusting the reference value to the timing of the signal received from 1 of the second source, so that the timing of the received signal is adjusted so that the time is closest to the unadjusted reference value Use; and synchronize the signal to the reference value for transmission.   27. The computer readable medium of claim 26, wherein the reference value is adjusted after no more signals from the first source are received.   28. The computer readable medium of claim 27, wherein adjustment of the reference value uses synchronized signal timing to determine the reference value after no more signals from the first source are received. To do.   27. The computer readable medium of claim 26, wherein the signal received from the first source comprises a frame, and the unadjusted reference value corresponds to the start of the frame.   30. The computer readable medium of claim 29, wherein the signals received from the second source each comprise a frame, and the adjusted reference value is the second closest to the unadjusted reference value in time. Corresponds to the start of the frame for source one.   27. The computer readable medium of claim 26, wherein the signal received from the first source comprises a plurality of multipath arrivals, wherein the unadjusted reference value is the first multipath in time. Corresponding to arrival.   32. The computer readable medium of claim 31, wherein the signal received from the second source comprises each of a plurality of multipath arrivals, wherein the adjusted reference value is an unadjusted reference value. Corresponds to the first multipath arrival of one of the second sources closest in time.   33. The computer readable medium of claim 32, wherein the signals received from the first and second sources each comprise a frame, and wherein the unadjusted reference value is received from the first source Corresponding to the start of the frame for the first multipath arrival of the signal, and the adjusted reference value is relative to the first multipath arrival for one of the second sources closest in time to the unadjusted reference value Corresponds to the start of the frame.   33. The computer readable medium of claim 32, wherein the signals received from the first and second sources each comprise a pilot signal, and the method uses the first and second using the respective pilot signals. Further comprising determining the timing of multipath arrival from the source and using the determined timing to demodulate the signals received from the first and second sources, wherein the reference value Adjusting comprises using the multipath arrival timing to identify one first multipath arrival of the second source closest in time to an unadjusted reference value. A device comprising:
Reference means for setting a reference value corresponding to the timing of the signal received from the first source;
Means for determining timing for each of the signals received from the plurality of second sources;
Adjusting means for adjusting the reference value to the timing of the signal received from 1 of the second source, wherein the timing of the received signal is adjusted so that the time is closest to the unadjusted reference value Means for synchronizing the signal to a reference value for transmission.   36. The apparatus of claim 35, further comprising means for receiving signals from the first and second sources.   36. The apparatus of claim 35, further comprising transmission means for transmitting a synchronized signal.   36. The apparatus of claim 35, further comprising transmitting means for transmitting a synchronized signal after the reference value.   40. The apparatus of claim 38, further comprising means for generating a trigger offset in time from a reference value, wherein the trigger is used by a transmitting means for transmitting a synchronized signal.   40. The apparatus of claim 39, wherein the transmitting means further comprises buffer means for storing the synchronized signal, wherein the buffer means emits the synchronized signal for transmission in response to the trigger. Configured.   36. The apparatus of claim 35, wherein the adjusting means adjusts the reference value after no more signals from the first source are received.   42. The apparatus of claim 41, wherein the adjusting means further comprises means for determining an adjustment of the reference value from the timing of the synchronized signal after no more received signals from the first source are received. To do.   36. The apparatus of claim 35, wherein the signal received from the first source comprises a frame, and wherein the referencing means sets the reference value to coincide with the start of the frame.   44. The apparatus of claim 43, wherein the signals received from the second source each comprise a frame, and wherein the adjusting means is one of the second sources closest in time to an unadjusted reference value. Adjust the reference value to match the start of the frame for.   36. The apparatus of claim 35, wherein the signal received from the first source comprises a plurality of multipath arrivals, wherein the reference means references to match the first multipath arrivals in time. Set the value.   46. The apparatus of claim 45, wherein the signal received from the second source each comprises a plurality of multipath arrivals, wherein the adjusting means is the second closest to the unadjusted reference value in time. The reference value is adjusted to match the first multipath arrival of one of the sources.   48. The apparatus of claim 46, wherein the signals received from the first and second sources each comprise a frame, and wherein the reference means is a first multipath of the signals received from the first source. Set a reference value to coincide with the start of the frame for arrival and to correspond to the start of the frame for the first multipath arrival for one of the second sources closest in time to the unadjusted reference value Adjust the reference value to. 48. The apparatus of claim 46, wherein the signals received from the first and second sources each comprise a pilot signal, the apparatus using the respective pilot signals from the first and second sources. Means further comprising means for determining the timing of multipath arrival and means for demodulating signals received from the first and second sources using the timing of multipath arrival; The means adjusts the reference signal by using the determined timing of multipath arrival for one of the second sources that is closest in time to the unadjusted reference value.

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